1. Field of the Invention
The present invention relates to a cleaning apparatus which cleans an image bearing member, a process cartridge having the cleaning apparatus, and an image forming apparatus.
2. Description of the Related Art
Some conventional cleaning apparatuses pressurize cleaning blades against image bearing members using compression springs (U.S. Pat. No. 4,712,946 (U.S. Patent Application Publication No. 2002/0025181 A1) (Patent Document 1) and U.S. Pat. No. 4,048,682 (Patent Document 2)). Using compression springs provides more precise pressures than using tension springs. Further, in case of tension springs, a blade plate end portion generally applies a pressure, and a cleaning blade pressure decreases in a blade center portion.
However, according to Patent Documents 1 and 2, when a plurality of compression springs is used in a longitudinal direction of the cleaning blade, depending on phases of the compression springs in a circumferential direction (positions of the compression springs in the circumferential direction), a pressurizing force of each compression spring varies, and variation in the pressurizing force in the longitudinal direction is produced. This reason is as follows. When biasing forces of springs do not work as in FIG. 11B, end portions of spirals of the springs are likely to abut on a seating plane. By contrast with this, at a position of the phase shifted 180 degrees from the end portion, the springs are likely to float from the seating plane. Hence, pressurizing forces of the springs in the circumferential direction. Therefore, when the phases of the springs are different, a position at which the highest pressurizing forces of the springs are produced in the circumferential direction changes. Meanwhile, phases of the compression springs in a rotation direction indicate at which position in the circumferential direction of the compression springs distal ends of the compression springs (end portions of the screw portions) are positioned with respect to a cleaning blade to be pressurized or a casing frame to which the compression springs are attached.